When I started reading astronomy books, in the 1960s, nobody knew if there existed planets around other stars and the common view was that they were very rare. Of course, that contrasted with the main theme of the science fiction of the time, of which I was also an avid reader. The idea that planetary systems were common in the galaxy was much more fascinating than the "official" one but, at that time, it seemed to be pure fantasy. But it turns out that science fiction was absolutely right, at least on this point. We are discovering hundreds of planets orbiting around stars and the latest news are that one sun-class star out of three may have an earth-like planet in the habitable zone. Fantastic!

The measurements that are telling us of extra-solar planets cannot tell us anything about extra-solar civilizations, another typical theme of science fiction. But, if earth-like planets are common in the galaxy, then organic, carbon based life should common as well. And if life is common, intelligent life cannot be that rare. And if intelligent life is not rare, then there must exist alien civilizations out there. With 100 billion stars in our galaxy, we may think that also on this point science fiction might have been right. Could the galaxy be populated with alien civilizations?

Here, however, we have a well known problem called the "Fermi Paradox". If all those civilizations exist, then could they develop interstellar travel? And, in this case, if there are so many of them, why aren't they here? Of course, for all we known the speed of light remains an impassable barrier. But, even at speeds slower than light, nothing physical prevents a spaceship from crossing the galaxy from end to end in a million year or even less. Since our galaxy is more than 10 billion years old, intelligent aliens would have had plenty of time to explore and colonize every star in the galaxy, jumping from one to another. But we don't see aliens around and that's the paradox. The consequence seems to be that we are alone as sentient beings in the galaxy, perhaps in the whole universe. So, we seem to be back to some old models of the solar system that told us that we are exceptional. Once, we were told that we are exceptional because planets are rare, now it may be because civilizations are rare. But why?

I mean no disrespect to Mr. Bardi (I think he's one of the better authors on the more pessimistic side of Peak Oil authors), but I have to laugh when people push their viewpoints under the banner of the "Fermi Paradox". I'm not suggesting Bardi has done anything nefarious here, but it's pretty evident the Fermi Paradox is often used to defend someone's particular viewpoint or otherwise doomsday scenario (Remember when it was used as a justification why we'd blow ourselves up with nuclear weapons?). The simple fact is the "paradox" is derived from the Drake equation...which is *not* sound science! Several terms in the equation are largely or entirely based on conjecture. Michael Crichton was spot on I think on the Drake Equation (even if he was WAY wrong on other things, such as climate change). It's essentially meaningless.

I could go on further about the problems with the whole "Why haven't we met any alien civilizations...well it must be because they destroyed themselves!", but I think I'll just leave it at that :)